Ferro-alloys and method of producing them



April 16, 1940. H. v. GLUNZ ET AL FERRO-ALLOYS AND METHOD OF PRODUCING THEM Filed Nov. 30, 1938 IN VENT ORS a 21 II 'I I m ATTORNEYS Patented Apr. 16, 1940 UNITED STATE FERRO-ALLOYS AND IHETHOD OF PRODUCING THEM Huck V. Glunz, Duncan Falls,

Painter, Zanesville, Ohio,

and Ernest Clifton assignors to Ohio Ferro-Alloys Corporation, Philo, Ohio, a corporation of Ohio Application November 30, 1938, SerialNo. 243,208

6 Claims.

The invention relates to ferro-alloys and methods of casting them. As used throughout this specification, and in the claims, term-alloy"- designates specifically an alloy of iron and tungsten, silicon, chromium, manganese, or the like, which is added to or introduced into molten irons and steels for deoxidizing them or for alloying purposes. Such alloys contain relatively large percentages of the non-ferrous metals, as for example ferro-chromium contains from about 65 to 75 per cent of chromium, and ferro-sllicon contains from about 50 to 90 per cent of silicon, substantially the entire remainder of each being iron.

Ferro-alloys are customarily produced in electric furnaces at temperatures materially higher than those used in melting of irons and steels. For example, the tapping temperature of a 50 per cent ferro-silicon is customarily in the neighborhood of 2950" F., and higher. At these high temperatures ferro-alloys have such solvent actions upon metals, such as gray iron and steel, which have been used for the manufacture of molds for casting irons and steels, that the ferroalloys rapidly cut through the molds if the casting procedure is the same as used for irons and steels. Because of this, among other factors,

ferro-alloys are customarily cast in sand molds whose surfaces may or may not be bonded by a binder, such as sodium silicate. Sand molds have fixed rates of cooling which are relatively slow and are characteristic of the materials of which they are formed. Because of this, there is frequently little or no time between furnace heats for removing and preparing mold beds for the next castias a consequence of whichlarge floor areas with attending expenses are neces- A further prejudicial consequence attending the casting of ferro-alloys in sand molds is the lack 'of cleanliness of the castings arising from foreign inclusions, such as slag, oxides, and the like, and also from mold material. As to the latter, so much mold-forming material adheres to the surfaces of the castings that .it is necessary to clean them with chipping hammers, brushes and the like before the metal can be used because, if the castings were not clean, the foreign material adhering to them would preiudicially aifect the iron or steel into which the ferro-alloy is introduced. Such cleaning necessarily adds to the costs of production.

Still further disadvantages attending the casting of ferro-alloys insand molds appear in the resulting castinss. The relatively slow rate of cooling of the castings results in their being of a porous or spongy character which adds to the bulk of given masses of ferro-alloys. Disintegration of slowly cooled sand-mold castings, as for example those of 50 per cent ferro-silicon, commonly takes place when they are subjected merely to atmospheric conditions for a material length of time, such as two or three months. Not only is the metal porous, but, due to its slow rate of cooling in sand molds, segregation difliculties m frequently arise. In other words, the metal is not homogeneous throughout, so that when the castings are broken into lumps for use, the lumps do not uniformly have the same relative contents of their deoxidizing or alloying constituents.

The object of our invention is to provide a method of casting ferro-alloys which overcomes the difficulties incident to the prior methods of casting them, and which results in the production of castings which are clean, substantially solid throughout, strong, and relatively stable against customary-disintegration when subjected to atmospheric conditions, and in which segregation is very materially reduced or eliminated. A further object is to provide a ferro-alloy casting which as cast is substantially free from occluded impurities, such as adhering particles of moldforming material, and which is solid and stable.

Our invention is predicated primarily upon our discovery that by casting ferro-alloys in the manner hereinafter explained the castings are strong, solid, stable, clean and substantially free from segregation.

In the practice of our invention a molten fermalloy is poured into a solid mold formed of a heat-conducting material such as carbon or graphite, but which is preferably a metal such as copper and gray iron. Preferably, the molten metal, which is tapped from a furnace at a high temperature, is placed in a reservoir. in which it is maintained until its temperature is reduced below that at which the metal has an active solvent action on the metal of which the casting molds are formed. Such lowering of the temperature of the molten metal also tends strongly to lessen the fire-cracking of the mold. While the amount of temperature reduction varies with particular ferro-alloys', by way of example a per cent ferro-silicon may be reduced from a temperature of about 2950 to about 2550 F. be- 50 fore it is cast. When cast in the mold, heat from the initial portion of the metal. poured into the mold is abstracted through the mold rapidly to solidify the mold-contacting shell or layer of the metal, and heat from the remainder of the metal is abstracted atsuch a controlled rate that the resulting casting has the above stated characteristics. During the casting operation there is preferably effected such relative movement between the stream of molten metal and the mold surface as to cause the metal to impinge upon difierent portions of such surface. This may be done either by moving the mold with relation to the stream of metal or by moving the stream of metal over the surface of the mold. However, it is preferably done by maintaining the stream in one position and suitably rotating the mold so that the metal falls upon an annular band of the bottom of the mold adjacent to its edge. Thus a layer of molten metal quickly spreads over the surface of the mold through which heat is so abstracted as to solidify it rapidly. In so pouring the metal, it does not impinge upon a small area of the surface of the mold for a sumcient length of time to permit the metal to exert its solvent action upon the mold, and hence the metal does not impair or destroy the mold.

The cooling of the metal in the manner Just explained may be eifected by properly proportioning the mold and its wall thickness. In addition to this, a cooling medium, such as water, is preferably applied to the exterior of the mold and to its support.

The invention will be further explained with reference to the accompanying drawing which is a vertical central cross-sectional view through a casting mold positioned in a tank of cooling water. 7

Having reference to the drawing, a mold I, which is preferably made of solid copper, is supported upon a turntable 2 which is provided with a ring gear 3 that meshes with a pinion 4 attached to a driving shaft 5 extending through a suitable packing gland 6 in the wall of a tank 1. The arrangement is such that during a pouring operation mold I may be so rotated that a stream ID of molten ferro-alloy impinges progressively upon an annular area of the outer portion of the mold. The speedof, rotationof the mold is relatively slow, as for example from 5 to 15 revolutions per minute for a mold that is 66 inches in diameter. Accordingly, the cast metal spreads out evenly upon the surface of the mold and is not subjected to any such centrifugal force during solidification as to effect segregation of the solidus from the liquidus during freezing. To abstract heat from the metal through the mold in the manner and for the purpose explained, the bottom of the mold is substantially immersed in a body of cooling water in tank 1, supplied to the tank by an inlet pipe II and removed from it through an overflow passage l2, and cooling water is sprayed upon the outer side wall of the mold from annular pipes l3. In cases where it is unnecessary artificially to cool the'mold, tank I may be omitted.

By way of example, and not of limitation of the scope of our invention, we here describe the casting of a percentferro-silicon alloy to form castings thereof having the characteristics and advantages that we have explained. The ferro-silicon was produced in an electric arc furnace, from which approximately 3% tons was tapped at a temperature of approximately 3000 F. into a reservoir in which it was maintained until it had cooled to approximately 2500 F. The thus cooled metal was then poured into copper molds formed and mounted as illustrated in Fig. 1. Each mold had a diameter of 66 inches and a depth of 9 inches, and its wall thickness varied as shown from about 3 inches at its edge to about 11 inches at its bottom. During the pouring of the metal, and until it solidified, each mold was rotated on its vertical axis at about six revolutions per minute. In this way the stream of molten metal impinged progressively upon an annular area near the edge of the mold. Heat was rapidly extracted from the layer of molten metal which first contacted the surface of the mold to form a shell or casing which, in effect, was a supplemental mold on which the further molten metal was poured. The rate of cooling thus effected was such as to cool the molten metal into a solid stable casting in about ten minutes, at which time the castings were removed from the mold. During the casting water was sprayed upon the outer face of the outwardly flaring side of the mold from air annular pipe 72 inches in diameter drilled with inch holes spaced about 3 inches.

As indicated, the foregoing data are given as a specific example of how the invention may be practiced in the casting of 50 per cent ferrosilicon alloy. Within the scope of the appended claims suitable variations may be made in the casting of other ,ferro-alloys to attain the ad-' vantages of our invention.

We claim:

1. In a method of casting a molten ferro-alloy.

to produce solid ferro-alloy for use in the manufacture of alloy irons and steels, the improvement comprising pouring a stream of the molten ferro-alloy upon the surface of a heat-conductingmold, effecting relative horizontal movement between said stream and the mold surface to cause the metal to impinge upon different portions of said surface but without substantial centrifugal movement of said ferro-alloy, and abstracting heat from the ferro-alloy metal through the mold rapidly to solidify the mold-contacting shell'of the ferro-alloy metal, and then to solidify the ferro-alloy poured upon said shell and thereby form a casting of the ferro-alloy in a dense,

strong and relatively stable condition.

2. A method according to claim .1, said mold being a metal mold.

3. A method according to claim 1, said mold being of metal and rotated on its vertical axis.

4. In a method of casting a molten ferro-alloy to produce solid ferro-alloy for use in the manufacture of alloy irons and steels, the improvement comprising pouring a stream of the molten ferroalloy upon the outer portion of the surface of a massive copper mold, rotating the mold slowly on its vertical axis to cause the metal progressively to impinge upon an outer annulus of the mold surface and to flow toward the surface of the mold without causing substantial centrifugal movement of' the ferro-alloy, and abstracting heat from the ferro-alloy metal through the "mold rapidly to solidify the mold-contacting shell of the ferro-alloy metal, and then to solidify the ferro-alloy poured upon said shell and thereby form a casting of the ferro-alloy in a dense, strong and relatively stable condition.

5. As a new article of manufacture, a cast body of a ferro-alloy which as cast is substantially free from surface and included foreign matter impurities, is solid throughout its mass, and is stable against disintegration, said body resulting from solidification of said, ferro-alloy from the liquid state by pouring it in a stream upon the surface of a heat-conducting mold while effecting relative movement between the stream and the mold and rapidly solidifying the I stable against disintegration, said body resulting from solidification of said ferro-silicon from the liquid state by pouring it in a stream upon the surface 01! a heat-conducting mold while efi'ecting relative movement between the stream and the mold and rapidly solidifying the ferro-silicon by abstracting heat from it througout the mold. 5

HUCK v. GLUNZ. ERNEST CIJFTON PAINTER. 

